UICollectionView and NSFetchedController Delegate Snippet

delegate.m

- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
  _sectionChanges = [[NSMutableArray alloc] init];
  _itemChanges = [[NSMutableArray alloc] init];
}

- (void)controller:(NSFetchedResultsController *)controller
  didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
           atIndex:(NSUInteger)sectionIndex
     forChangeType:(NSFetchedResultsChangeType)type {
  NSMutableDictionary *change = [[NSMutableDictionary alloc] init];
  change[@(type)] = @(sectionIndex);
  [_sectionChanges addObject:change];
}

- (void)controller:(NSFetchedResultsController *)controller
   didChangeObject:(id)anObject
       atIndexPath:(NSIndexPath *)indexPath
     forChangeType:(NSFetchedResultsChangeType)type
      newIndexPath:(NSIndexPath *)newIndexPath {
  NSMutableDictionary *change = [[NSMutableDictionary alloc] init];
  switch(type) {
    case NSFetchedResultsChangeInsert:
      change[@(type)] = newIndexPath;
      break;
    case NSFetchedResultsChangeDelete:
      change[@(type)] = indexPath;
      break;
    case NSFetchedResultsChangeUpdate:
      change[@(type)] = indexPath;
      break;
    case NSFetchedResultsChangeMove:
      change[@(type)] = @[indexPath, newIndexPath];
      break;
  }
  [_itemChanges addObject:change];
}

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
  [self.collectionView performBatchUpdates:^{
    for (NSDictionary *change in _sectionChanges) {
      [change enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
        NSFetchedResultsChangeType type = [key unsignedIntegerValue];
        switch(type) {
          case NSFetchedResultsChangeInsert:
            [self.collectionView insertSections:[NSIndexSet indexSetWithIndex:[obj unsignedIntegerValue]]];
            break;
          case NSFetchedResultsChangeDelete:
            [self.collectionView deleteSections:[NSIndexSet indexSetWithIndex:[obj unsignedIntegerValue]]];
            break;
        }
      }];
    }
    for (NSDictionary *change in _itemChanges) {
      [change enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
        NSFetchedResultsChangeType type = [key unsignedIntegerValue];
        switch(type) {
          case NSFetchedResultsChangeInsert:
            [self.collectionView insertItemsAtIndexPaths:@[obj]];
            break;
          case NSFetchedResultsChangeDelete:
            [self.collectionView deleteItemsAtIndexPaths:@[obj]];
            break;
          case NSFetchedResultsChangeUpdate:
            [self.collectionView reloadItemsAtIndexPaths:@[obj]];
            break;
          case NSFetchedResultsChangeMove:
            [self.collectionView moveItemAtIndexPath:obj[0] toIndexPath:obj[1]];
            break;
        }
      }];
    }
  } completion:^(BOOL finished) {
    _sectionChanges = nil;
    _itemChanges = nil;
  }];
}

Courtesy of: http://jose-ibanez.tumblr.com/post/38494557094/uicollectionviews-and-nsfetchedresultscontrollers